Field of the Invention
The present invention relates to an image forming apparatus configured to form an image on a sheet.
Description of the Related Art
Generally, in an image forming apparatus such as a copier, a sheet is sometimes laterally displaced in a width direction of the sheet while being conveyed. In the case where an image is formed on the sheet laterally displaced, the image printed on the sheet is displaced from the center of the sheet. This may be perceived as printing of a poor quality. Therefore, a shifting mechanism that detects the position of an edge portion of the sheet in the width direction and corrects the lateral displacement of the position of the sheet is known.
In Japanese Patent Laid-Open No. 2009-143643, an image forming apparatus that detects the position of an edge portion of a first page sheet in the width direction and corrects the image formation position for a third page sheet on a photoconductor on the basis of the amount of displacement of the edge portion of the first page sheet from a standard position is proposed. This image forming apparatus corrects the image formation position in advance on the basis of the amount of displacement of a sheet of two pages before, and thereby reduces the shift amount of the sheet to improve the image quality and the productivity of the image forming apparatus.
However, although the image forming apparatus disclosed in Japanese Patent Laid-Open No. 2009-143643 uses a detection result of an edge portion of a preceding sheet for determining the image formation position of a following sheet, the image forming apparatus does not change the image formation position between the first surface and the second surface of the sheet. Typically, the displacement of the position of an edge portion of a sheet in the width direction may occur during a duplex conveyance process of inverting and conveying the sheet for duplex printing, that is, after an image is formed on the first surface of the sheet and before the sheet reaches a registration roller pair again.
Thus, in the image forming apparatus disclosed in Japanese Patent Laid-Open No. 2009-143643, the shift amount for the second surface increases by an amount corresponding to the amount of displacement of the sheet in the width direction during the duplex printing process. This may lower the productivity and the image quality.